On Mon, Apr 22 2019, Jeff Layton wrote:
> After a blocked nfsd file_lock request is deleted, knfsd will send a
> callback to the client and then free the request. Commit 16306a61d3b7
> ("fs/locks: always delete_block after waiting.") changed it such that
> locks_delete_block is always called on a request after it is awoken,
> but that patch missed fixing up blocked nfsd request handling.
>
> Call locks_delete_block on the block to wake up any locks still blocked
> on the nfsd lock request before freeing it. Some of its callers already
> do this however, so just remove those calls.
>
> URL: https://bugzilla.kernel.org/show_bug.cgi?id=203363
> Fixes: 16306a61d3b7 ("fs/locks: always delete_block after waiting.")
> Reported-by: Slawomir Pryczek <slawek1211@xxxxxxxxx>
> Cc: Neil Brown <neilb@xxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> fs/nfsd/nfs4state.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 6a45fb00c5fc..e87e15df2044 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -265,6 +265,7 @@ find_or_allocate_block(struct nfs4_lockowner *lo, struct knfsd_fh *fh,
> static void
> free_blocked_lock(struct nfsd4_blocked_lock *nbl)
> {
> + locks_delete_block(&nbl->nbl_lock);
> locks_release_private(&nbl->nbl_lock);
Thanks for tracking this down.
An implication of this bug and fix is that we need to be particularly
careful to make sure locks_delete_block() is called on all relevant
paths.
Can we make that easier? My first thought was to include the call in
locks_release_private, but lockd calls the two quite separately and it
certainly seems appropriate that locks_delete_block should be called
asap, but locks_release_private() can be delayed.
Also cifs calls locks_delete_block, but never calls
locks_release_private, so it wouldn't help there.
Looking at cifs, I think there is a call missing there too.
cifs_posix_lock_set() *doesn't* always call locks_delete_block() after
waiting. In particular, if ->can_cache_brlcks becomes true while
waiting then I don't think the behaviour is right.... though I'm not
sure it is right for other reasons. It looks like the return value
should be 1 in that case, but it'll be zero.
But back to my question about making it easier, move the BUG_ON()
calls from locks_free_lock() into locks_release_private().
??
Thanks,
NeilBrown
> kfree(nbl);
> }
> @@ -293,7 +294,6 @@ remove_blocked_locks(struct nfs4_lockowner *lo)
> nbl = list_first_entry(&reaplist, struct nfsd4_blocked_lock,
> nbl_lru);
> list_del_init(&nbl->nbl_lru);
> - locks_delete_block(&nbl->nbl_lock);
> free_blocked_lock(nbl);
> }
> }
> @@ -4863,7 +4863,6 @@ nfs4_laundromat(struct nfsd_net *nn)
> nbl = list_first_entry(&reaplist,
> struct nfsd4_blocked_lock, nbl_lru);
> list_del_init(&nbl->nbl_lru);
> - locks_delete_block(&nbl->nbl_lock);
> free_blocked_lock(nbl);
> }
> out:
> --
> 2.20.1
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